Capture of Perfluorooctanoic Acid Using Oil-Filled Graphene Oxide–Silica Hybrid Capsules
Muthana Ali, Shane P. Meaney, Luke W. Giles, Phillip Holt, Mainak Majumder, Rico F. Tabor
Abstract
Fluorinated hydrocarbon (FHC) contamination has attracted global attention recently because of persistence within the environment and ecosystems of many types of FHC. The surfactant perfluorooctanoic acid (PFOA) is particularly commonly found in contaminated sites, and thus, urgent action is needed for its removal from the environment. In this study, water dispersible hybrid capsules were successfully prepared from an oil-in-water emulsion stabilized by graphene oxide and including a silicate precursor to grow a strong, mesoporous capsule shell surrounding the droplets. These capsules were decorated with amine groups to present a positively charged outer corona that attracts negative PFOA molecules. The aminated capsules were effectively applied as a novel technology to adsorb and sequester PFOA contamination in water. It was confirmed that PFOA removal by the capsules was pH and PFOA concentration dependent, with adsorption efficiencies of >60 mg g–1 under ideal conditions. PFOA removal kinetics followed using high-performance liquid chromatography and liquid chromatography–mass spectrometry showed that capture of PFOA by the capsules reached a maximum of >99.9% in 2–3 days.